Growth, development and mineral content of apple fruit in different water status conditions

Three water status conditions (no deficit, mild deficit and high deficit) were applied to trees of apple cv. 'Granny Smith' growing in pots during two periods of four weeks (the last phase of fruit growth by cell division and the middle phase of fruit growth by cell enlargement). In the fruit cell division phase (first period) water deficit reduced fruit growth by decreasing water uptake and increasing the percentage dry matter; protein and acid hydrolyzable polysaccharides (mainly starch and hemicellulose) accumulation seemed not to be affected. There was no activation of mechanisms useful in adjusting the osmotic potential through the synthesis and on the translocation of soluble sugars and K+. In the fruit cell enlargement phase (second period) water deficit reduced fruit growth by decreasing water uptake, and to a greater extent dry-matter accumulation. Acid hydrolyzable polysaccharide accumulation was also affected. Accumulation of alkali-soluble protein increased when the stress situation was higher and when a previous deficit was imposed. Moreover, there was an activation of mechanisms useful in adapting the cell osmotic potential (translocation and/or synthesis): accumulation of soluble sugars, amino acids and K+; the effects on these two last compounds appeared to be related to the time when a water deficit in the first period was imposed. The increase in water deficit acted in both periods by increasing the inhibitory effect as well as the resistance mechanisms.